1. Field of the Invention
This invention relates to digital-to-analog (D/A) converters. More particularly, this invention relates to such converters having a high resolution, such as 18 bits, and which yet are capable of operating from a single supply voltage.
2. Description of the Prior Art
D/A converters capable of 12-bit to 16-bit conversions are commonly available, and take various forms. One popular 12-bit converter, using individual current sources for each bit, is disclosed in U.S. Pat. No. 4,309,693 (Craven). A 16-bit converter using cascaded resistor strings is disclosed in U.S. Pat. No. 4,543,560 (Holloway).
For modern high-performance applications such as digital audio systems, it is desired to make still higher resolution conversions, up to at least 18 bits. Moreover, it is very important that such a converter be operable with a single supply voltage, such as 5 volts. The converter also must have very low distortion, and be capable of integration with all required functions on a single chip.